Standalone purchases receive all updates until the next major release. Historically that has run parallel to Windows releases, though it's hard to say how that'll work now with Windows 10 being 'permanent'.
ODNT gets you more products, and all updates (including major releases) so long as your subscription is active. You can keep what you've downloaded and continue to use it after your subscription expires, but you won't be eligible for any updates released after that.
